Results 1 to 2 of 2

Math Help - Trig Identity Problem

  1. #1
    Newbie
    Joined
    May 2009
    From
    Nevada
    Posts
    3

    Trig Identity Problem

    Just started trig, please show step by step.
    1> cos 19pi / 12 using Half-Angle Identites

    2> cos 165* using Half-Angle Identites

    any help would be greatly appreciated!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,698
    Thanks
    454
    Quote Originally Posted by Daniels4691 View Post
    Just started trig, please show step by step.
    1> cos 19pi / 12 using Half-Angle Identites

    2> cos 165* using Half-Angle Identites

    any help would be greatly appreciated!
    \cos\left(\frac{x}{2}\right) = \pm \sqrt{\frac{1 + \cos{x}}{2}}

    in addition to the half-angle identity, you need the folowing information ...

    \frac{19\pi}{12} is in quadrant IV, which tells you the sign of the cosine value.

    \frac{19\pi}{12} is half of \frac{19\pi}{6}

    \frac{19\pi}{6} is coterminal with \frac{7\pi}{6} , which means their respective cosine values are the same.

    \cos\left(\frac{7\pi}{6}\right) is a unit circle value.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trig Identity Problem
    Posted in the Trigonometry Forum
    Replies: 6
    Last Post: September 7th 2011, 02:08 PM
  2. Another Trig Identity problem.
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: November 28th 2010, 08:53 PM
  3. Trig identity problem
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: December 18th 2008, 08:23 PM
  4. Trig identity problem
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: November 9th 2007, 09:37 PM
  5. Help with a Trig Identity Problem
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: June 30th 2007, 08:22 AM

Search Tags


/mathhelpforum @mathhelpforum